Fertilizer particles described herein include a powder composition that can contain one or more urease inhibitors and/or nitrification inhibitors and a filler material embedded within a solid urea matrix. Methods of producing the fertilizer particles involve contacting a powder composition that can contain one or more urease inhibitors and/or nitrification inhibitors and a filler with molten urea under conditions sufficient to form a fertilizer particle having the powder composition embedded within a solid urea matrix.